Catalytic reforming process with sulfur removal

ABSTRACT

An improved catalytic reformer system wherein chloride compounds are removed from the feed, sulfur compounds contained in the total feed are converted to H2S in a hydrodesulfurization zone and the H2S is removed in an adsorbing zone containing a solid adsorbent.

United States Patent 1191 Louder et a1.

[ 1 Aug. 5, 1975 1 1 CATALYTIC REFORMTNG PROCESS WITH SULFUR REMOVAL [751 Inventors: Kenneth E. Louder. Wilmington.

De1.; William A. Ackerman; Irene F. Kress. both of Media. Pa.

[73] Assignee: Sun 011 Company 01 Pennsylvania, Philadelphia. Pa.

[22] Filed: Nov. 23. 1973 [21] Appl. No.: 418,504

51 1m. 0.. ClOg 25/00;C10g 23/O0;C10g 31/14 [58] Field of Search 208/88, 39 91 99, 102. 208/138. 139. 134. 211, 213. 262

[56] References Cited UNITED STATES PATENTS 9/1950 Short 203/213 Primary Examiner-Delbert E. Gantz Assistant Examiner 1ames W. Hellwege Attorney, Agent, or F1'rmGeorge L. Church; Donald R Johnson; Paul Lipsitz 57 ABSTRACT An improved catalytic refonner system wherein chloride Compounds are removed from the feed, sulfur compounds contained in the total feed are converted to H. .S in a hydrodesulfurization zone and the H5 is removed in an adsorbing zone containing a solid adsorbent.

6 Claims, 1 Drawing Figure CATALYTIC REFORMING PROCESS WITH SULFUR REMOVAL BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to improvements in the catalytic reforming of naphthas. More particularly, it relates to the removal of residual sulfur, organic sulfur compounds and H 5, from partially pretreated reformer feed by either treatment of the total reformer feed including hydrogen recycle or treatment of the hydrogen recycle alone utilizing desulfurization catalysts and/or an adsorbent such as zinc oxide to remove sulfur, especially hydrogen sulfide, from said streams.

2. Description of the Prior Art The higher boiling part of the gasoline fraction contained naturally in crude oil has such a low octane number that it is necessary to convert it to higher octane number gasoline by the process of catalytic reforming. Likewise, l80-400F. heavy gasoline produced by hydrocracking has a low octane and it too must be reformed. Reforming of heavy, or selected fractions, of catalytically cracked gasoline is also practiced to improve its octane number.

Many catalytic reforming processes are commercially available such as Platforming (UOP), Ultraforming (Std. Indiana), Houdryforming (Houdry Process and Chemical Co), Catforming (Atlantic), Powerforming (Esso) and others. These reforming processes are basically all the same, at least with respect to the reactions which occur such as dehydrogenation of napthenes, e.g., cyclohexane being converted into benzene and hydrogen, dehydroisomerization of naphtenes with side chains, e.g., dimethylcyclopentane being converted to methylcyclohexane and then to toluene, dehydrocyclization of parafiins, e.g., n-hexane is con verted into cyclohexane and then to benzene, isomerization of paraffms, e.g., heptane going to methylhexane, cracking and hydrogenation of paraffin, e.g., decane cracking and combining with hydrogen to produce normal and isopentane, hydrogenation of any olefins present and hydrodesulfurization of sulfur compounds, eg, thiophene plus hydrogen resulting in hydrogen sulfide and butanes. The dehydrogenation of naphthenes occurs very rapidly in the catalytic reforming process, and the isomerization of naphthenes and paraffins is also quite rapid. Thus, these reactions predominate and slower cyclization and hydrocracking reactions be come significant mainly at severe conditions of low space velocity, high pressure and high temperature. Cyclization favors a low temperature. Since hydrogenation and dehydrogenation occur at the same time, the production of hydrogen, which is recycled in the pro cess, is available for the hydrogenation reactions. Most processes use a platinum catalyst which contains between 0.3 and 0.8% platinum, and up to 1% of a halogen may be used as a promoter to regulate the acidity at the cracking and isomerization sites on the alumina support of the catalyst.

For best performance, catalytic reformers upgrading low octane naphtha to high octane gasolines require low sulfur levels in the feed, preferably less than 1 ppm. Some reformers are equipped with feed desulfurizers that cannot achieve the desired low sulfur levels because of temperature or hydrogen recycle limitation or poor hydrogen sulfide stripping. Considerable expense is usually encountered in trying to correct these limitations, and in some cases it means installing a new desulfurization plant and in others a large stripping column.

SUMMARY OF THE INVENTION It has now been found that residual sulfur can be removed from partially pretreated reformer feed by passing the total reformer feed including hydrogen recycle over a bed of desulfurization catalysts followed by an adsorbent such as zinc oxide or over zinc oxide alone at temperatures preferably above 600F. In another embodiment, the adsorbent may be used alone downstream of any reformer reactor to adsorb H S produced from the conversion of sulfur compounds in the reformer section. In a further embodiment, the adsorbent may be used alone in the recycle hydrogen stream either before or after compression of said stream to remove hydrogen sulfide contained therein.

Therefore, it is an object of the present invention to provide an improved catalytic reforming process with enhanced sulfur removal so as to improve the upgrad ing of low octane naphtha taking place therein and to increase the life and enhance the activity of the catalyst being used, which is often very expensive.

It is a further object of the invention to provide a reforming process combined with an adsorbing process to remove hydrogen sulfide to levels of 0.2 ppm in re former feed as compared to 0.5 to l .0 ppm levels achieved in conventional strippers.

These and other advantages will be more readily understandable upon review of the detailed description which follows.

DESCRIPTION OF THE DRAWING The drawing shows the preferred flow diagram of the combination reforming-sulfur removing system of the present invention with the hydrodesulfurization catalyst bed-adsorbent bed being pictured upstream of the reformer feed heater, said location being preferred. Alternate locations for the adsorbent bed alone are shown at points A between the heater and the reformer reactor, B in the outlet stream of the reformer reactor before the liquid separator, C in the hydrogen recycle stream prior to the compression of said stream, and D in the hydrogen recycle stream between the compressor and the point where the recycle mixes with the naphtha feed. It is also envisioned that the adsorbent alone may be placed in a void space in an existing reformer reactor.

Naphtha feed usually containing between l-lO ppm of organic sulfur and/or H 8 enters the process through the feed line and is heated through heat exchange to temperatures of between 550 and 850F. at a pressure of from l50 to 650 psig. This heated naphtha feed then flows through a chloride removal zone 3 and via line 4, through a combination hydrodesulfurization catalyst bed and adsorbent bed wherein the normal lto l0 ppm organic sulfur is converted to H S which is then scavenged out of the naphtha stream together with H 8 entering with the feed and/or recycle H; by the adsorbent, preferably zinc oxide. The treated naphtha feed then passes via line 6 to the feed heater 7 wherein the temperature is raised to a level of 850 to 950F. or that required to meet objectives of reforming operation. The feed exits said heater through line 8 and enters the reformer reactor 9 which is of conventional configuration and contains commercially available platinum reform ing catalyst. These platinum reforming catalysts may contain second metals such as rhenium or iridium. Products leave the reformer reactor via line and pass into the product separator ll wherein the liquid product is withdrawn from the bottom and hydrogen recycle is taken overhead to be recycled and compressed tojoin the naphtha feed via line 12, compressor 13, and line 14. The combined naphtha feed hydrogen recycle then passes through the system as previously described.

Preferred location of the adsorbent-hydrodesulfurization unit is upstream of the furnace and it operates preferably above 600F. and treats total feed and hydrogen recycle to remove the sulfur contained therein. This location is preferred over location A since at temperatures of 850 to 950 hydroeracking reactions may occur over either the desulfurization catalyst or the adsorbent although location A is still operable and would achieve some of the advantages of the present invention. Location B, C and D are all operable and would separator wherein the liquid product is withdrawn and sent to storage for further processing and wherein the hydrogen is taken overhead, compressed, and recycled with the naphtha feed.

It is recognized that HCl in the reformer recycle gas can react with ZnO to form ZnCl which in turn can be carried into the reforming zone and adversely affect the catalyst. This problem is overcome by using a commerical chloride scavenger in this system such as a caustic solution in a pretreater or a copper catalyst guard case remove sulfur compounds converted to hydrogen sulled upstream of the ZnO bed. Copper on alziimma fide in the reformer catalyst from either the combined and F P Oxlde on alumma cdt'fllysis F i g products at location B or the hydrogen recycle at locaappl'cauons are z z g z g U tions C and D. The disadvantage of these locations not the 22,509 poullds y 3. 3 12; from present in location A is that some of the sulfur may re- 75 lyst fg g g g z main on the reformer catalyst making it less effective iS n S/ 0 il; i g t Zinc oxide or the hydrogen sulfide produced in the reformer see- O Owmg equl l r u pp tion might react with piping, etc., to form sulfides that Secuon' can be released into the catalyst system during regener Z S H O 2110 H 5 ation to poison the reformer catalyst. ln whatever loca- 3O the e uilibrium constant for the reaction is defined tion IS used. the 2110 bed is preceded by a chloride q scavenging zone. DH

While the primary objective is to keep sulfur from en- K 2 tering the reformer system. it is also desirable to keep 7 "H 0 the hydrogen sulfide concentration in the recycle hy 3 and varies with wmperawre as knows At 0 drogen as low as possible. The concentration of H 8 in (200C) K: S 0 X A 7520': (400C) K l 8 X the i i f gl g j g up to five nmesghc l0. A suitable zinc oxide adsorbent is available from Concen m m e epen mg upon Opera mg Katalco Corporation marked Katalco-lCL32-4 cataconditions and hydrogen production rate. Therefore, it lyst and is in granular form of 1A; in. to 3/16 in. diamfler becomes clear that an efficient adsorbent that includes 40 with a bulk density of 69 lbs /cu ft treating the recycle as is done in all cases herein will re- Table Shows a Series f ilot plant runs with a naph- Sult in hydrogen Sulfide Concgmrafions in the tha feed containing sulfur passed over zinc oxide to redrogen recycle than is possible with conventional feed move Sulfur from Said naphtha feed which is a typica| uieatmnt and Stripping The preferrelembodinjlcm as reformer feed. Table ll shows the composition of the dlscussed f the process flow d'agram wnh the feedstocks used in these pilot plant runs. Each stock hydrodesulfunzanon Catalyst bed and adsorbent bed has been run at a series of liquid hourly space velocities i' ufstreamhof t; feed l flf f d mbi d th and at a series of temperatures and ppm sulfur before;

n a Y em 511C 35 P 3 e6 CO and after are shown. As can be seen mm a review 0 hydrogen recycle, at ratios 0f 4:] to H-zlfeedi are 0 these pilot plant runs, the ZnO does a remarkable job fitfst P fwg o f ggg f ghf 39 3 5 5 in removing sulfur from reformer feed. This process has a a Pressure 0 0 P g- Com me 5 Team application not only in catalytic reforming but also in then enters first the hydrodesulfurization section which id phase d lf i ti Systems to complete lf contains either nickel molybdenum or cobalt molybderemoval i i r fi process sy tem where H 5 num desulfurizing catalyst. commercially available to stripping is not adequate and to desulfurize already refineriesv In this section sulfur compounds are conl wulfur streams in various refinery processes verted to hydrogen sulfide which is carried with the wherein ulfur is a problem TABLE I WtT/P S in" Liquid Hourly Temp. Feed Product Feedstock Run ZnO Bed Space Velocity F Sulfur ppm Sulfur ppm A 1 0 4 625 4.4 0.1 2 l 1.5% 4 625 4.4 1.7 3 l 1.5 4 625 4.4 0.8 4 l5.() 4 625 4.4 L5 5 0 I2 625 4.4 0.] 6 1.5 12 625 4.4 1.3 7 l l5 I2 625 4.4 [,2 x 15.0 12 625 4.4 2.2 9 (l 6 690 4.4 Ol 10 0 4 750 4.4 0.1

TABLE I -Continued Wtfir S in Liquid Hourly Temp. Feed Product Feedstock Run ZnO Bed Space Velocity F Sulfur ppm Sulfur ppm 1 1 11.5 4 750 4.4 0.2 12 15.0 4 750 4.4 0.3 13 0 12 750 4.4 0.1 14 H15 12 750 4.4 0.2 15 15.0 12 750 4.4 0.0 16 1 1.5 4 550 4.4 1.6 17 11.5 12 550 4.4 1.8 18 1 1.5 4 625 4.4 1.7 19 l 1.5 4 625 4.4 0.8 20 11.5 12 625 4.4 1.8 21 11.5 12 625 4.4 1.2 22 11.5 4 750 4.4 0.2 23 11.5 12 750 4.4 0.2 B 24 0 12 625 1.4 0.1 25 15.0 12 625 1.4 0.2 26 I50 4 625 1.4 0.4 27 0 4 750 1.4 0.3 A 28 15.0 4 625 4.4 1.5 29 15.0 12 625 4.4 2.2 30 15.0 4 750 4.4 0.3 31 15.0 12 750 4.4 0.0 B 32 0 4 625 1.4 0.4 33 0 I2 625 1.4 0.2

"94 S on catalyst increases due to ZnS hcing formed in the Zn() bed. The high levels here were artifically achieved \ia sulfur loading for the purpose of experimentation TABLE ll Feed A Feed B API Gravity 1'60 54.2 46.2 Sulfur, ppm 4.4 1.4 Distillation (Engler) initial 185 325 5% 208 346 109% 222 349 30% 254 50% 280 367 7071 309 907 343 410 95% 368 427 end point 414 450 "'Actuzll specifications not available. typical data for this refinery stream substituted ""Actual sulfur on sample used in tests on Table l.

wherein reforming of naphthas and conversion of sulfur compounds to H 8 takes place.

d. withdrawing from step (c) a gaseous stream to be recycled to step (a). and

e. withdrawing a reformed naphtha product from step (c).

2. The process of claim 1 wherein said catalytic reforming utilizes catalyst selected from the group consisting of platinum on alumina, platinum and rhenium on alumina, platinum and iridium on alumina and platinum, rhcnium and iridium on alumina.

3. The process of claim 2 wherein the hydrodesulfurization step utilizes a catalyst selected from the group consisting of cobalt-molybdenum on alumina and nickel-molybdenum on alumina.

4. The process of claim 3 wherein said chloride removal zone is a guard case containing a catalyst selected from the group consisting of copper on alumina and copper oxide on alumina.

S. The process of claim 4 wherein said adsorption takes place at a temperature in the range of 550 to 850F.

6. The process of claim 5 wherein the reforming catalyst is selected from the group consisting of platinum on alumina, platinum and rhenium on alumina, platinum and iridium on alumina and platinum, rhenium and iridium on alumina. the adsorbent is zinc oxide and the chloride removal zone is a guard case containing a catalyst selected from the group consisting of copper on UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENTNO. 3,898,153

DATED 1 August 5, 1975 INVENTOR( 1 Kenneth E. Louder, William A. Ackerman, Rene F. Kressts It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Change inventors name Irene F. Kress to Rene F. Kress.

Signed and Sealed this twenty-first D ay Of October 1 9 75 [SEAL] A nest:

RUTH C. MASON C. MARSHALL DANN Atresling Officer Commissioner nfParenrs and Trademarks 

1. A PROCESS FOR CATALYTICALLY REFORMING A NAPHTA FEED STREAM CONTAINING SULFUR AND CHLORIDE COMPOUNDS IN THE PRESSENCE OF HYDROGEN WHICH COMPRISES A. PASSING THE FEED AND A HYDROGEN RECYCLE THROUGH A CHLORIDE REMOVAL ZONE, B. PASSING THE CHLORIDE FREE FEED AND HYDROGEN RECYCLE THROUGH A HYDRODESULFURIZATION ZONE WHEREIN THE SULFUR IS CONVERTED TO H2S AND A PACKED BED GRANULAR ZINZ OXIDE ABSORBENT WHEREIN THE H2S IS ADSORBED, C. PASSING SAID DESULFURIZED FEED THROUGH A CATAYTIC REFORMING ZONE UNDER REFORMING CONDITIONS WHEREIN REFORMING OF NAPHTHAS AND CONVERSION OF SULFUR COMPOUNDS TO H2S TAKES PLACE, D. WITHDRAWING FROM STEP (C) A GASEOUS STREAM TO BE RECYCLED TO STEP (A), AND E. WITHDRAWING A REFORMED NAPHTHA PRODUCT FROM STEP (C).
 2. The process of claim 1 wherein said catalytic reforming utilizes catalyst selected from the group consisting of platinum on alumina, platinum and rhenium on alumina, platinum and iridium on alumina and platinum, rhenium and iridium on alumina.
 3. The process of claim 2 wherein the hydrodesulfurization step utilizes a catalyst selected from the group consisting of cobalt-molybdenum on alumina and nickel-molybdenum on alumina.
 4. The process of claim 3 wherein said chloride removal zone is a guard case containing a catalyst selected from the group consisting of copper on alumina and copper oxide on alumina.
 5. The process of claim 4 wherein said adsorption takes place at a temperature in the range of 550* to 850*F.
 6. The process of claim 5 wherein the reforming catalyst is selected from the group consisting of platinum on alumina, platinum and rhenium on alumina, platinum and iridium on alumina and platinum, rhenium and iridium on alumina, the adsorbent is zinc oxide and the chloride removal zone is a guard case containing a catalyst selected from the group consisting of copper on alumina and copper oxide on alumina. 